Larkspur Consumption Research Articles

PSII-17 Sheep Foraging Relative to Stock Density, Time of Day, and Sheep Type in a Poisonous Plant Context

Abstract Plains larkspur (Delphinium geyeri) is a poisonous plant species that can be highly toxic at certain growth stages on western Great Plains rangelands. Targeted sheep grazing has been proposed as a mitigation strategy to reduce larkspur abundance and poisoning risk for cattle due to their greater toxicological resilience to the diterpenoid alkaloids. We incorporated targeted-sheep grazing in a northern mixed-grass prairie with our objective to determine the influence of stocking density, time of day, and sheep type on foraging behavior. During May 2022, Dorper (< 1-year-old lambs, n = 123, BW 25 kg ± 0.4; and 3 to 6-year-old ewes, n = 14, BW 47 kg ± 1.8) and Rambouillet (3 to 6-year-old ewes, n = 13, BW 76 kg ± 2.9) sheep were used in three stocking density treatments 1) 120 AU/day (1 day in a 0.25 ha paddock), 2) 60 AU/day (2 days in a 0.5 ha paddock), and 3) 40 AU/day (1 day in a 0.75 ha paddock) that were replicated four times. Sheep were housed overnight in a common area. We observed bite counts daily for nine randomly chosen sheep (three from each category) over five-minute intervals, in the morning and afternoon. We used a generalized linear model to assess the fixed effects of sheep type (Rambouillet ewe vs. Dorper ewe; Dorper ewe vs. Dorper lamb) and stock density on bite counts. Least squared means were analyzed for stock density using Tukey test, and for breed and age using student’s T test. We observed contrasts between morning and afternoon sheep foraging and diet selection. Mechanistically, this is likely due to the introduction of sheep into a new paddock in the morning after confinement and satiation diluting differences in the afternoon. Sheep breed influenced the proportion of graminoids consumed (96.9% Rambouillet vs 99.3% Dorper, P = 0.02), but differences were not observed between Dorper ewes and lambs (P = 0.57). The proportion of forb bite counts did not differ between Dorper ewes and lambs (0.6% vs. 0.4%, respectively, P = 0.6), nor between the Dorper ewes and Rambouillet ewes, despite the latter having a 3.5-fold greater selectivity (2.1%, P = 0.08). Larkspur consumption was no different between Dorper ewes and lambs (0.04% ewes vs. 0.01% lambs, P = 0.48), nor between Dorper ewes and Rambouillet ewes (0.28%, P = 0.09). Stock density influenced forb consumption; the proportion of forb bite counts were 12 times greater in the 0.5 ha paddock (3%) compared with the 0.25 ha paddock (0.3%, P = 0.005). Despite all consuming > 95% grass in the diet, results indicate that Rambouillet sheep trended towards greater selectivity than Dorper sheep, and greater selectivity in light to moderate stock densities may increase the proportion of larkspur in sheep diets.

Mineral-salt supplementation to ameliorate larkspur poisoning in cattle.

Larkspurs (Delphinium spp.) are native forbs that are poisonous to cattle and cost livestock producers millions of dollars in losses each year. Macro and micro minerals are required for normal functioning of essentially all metabolic processes in ruminants. The role that mineral status may play in larkspur poisoning in cattle is not clear. In this study, we seek to determine the effects a mineral-salt supplement, commonly used by cattle producers, to potentially reduce cattle losses to larkspur. The ability of mineral-salt supplementation to alter susceptibility to larkspur toxicosis was evaluated in a pen study. Animals supplemented with mineral-salt were found to be less susceptible to larkspur poisoning than the non-supplemented animals. A separate group of animals were then grazed on larkspur infested rangelands. One group was supplemented with a mineral-salt mix and the other group did not receive any mineral-salt. Supplementing cattle with the mineral-salt mix did not alter larkspur consumption (P > 0.05). However, overall larkspur consumption was low and averaged 3 ± 1.0% and 2 ± 1.1% for cattle supplemented with mineral and non-supplemented, respectively. Serum was collected from animals once a week during the grazing study. Average and maximum serum concentrations of toxic larkspur alkaloids were numerically higher in mineral-salt supplemented cattle compared with the non-supplemented animals. Results from the pen study suggest that a good mineral supplementation program will provide a protective effect for animals grazing in larkspur-infested ranges. The mineral-salt supplemented steers, in the grazing study, were not observed to consume less larkspur than the non-supplemented animals; however, the mineral-salt supplemented animals had higher concentrations of larkspur alkaloids in their serum indicating they may be able to tolerate higher larkspur consumption. The data also indicate that mineral-salt supplementation must be continuous throughout the time the animals are grazing these rangelands as the positive effects can be lost within 30 d post supplementation.

Grazing of Delphinium occidentale (duncecap larkspur) by susceptible and resistant cattle

<h2>ABSTRACT</h2> <i>Delphinium</i> spp. (larkspurs) often fatally poison grazing cattle. Angus cattle differing in susceptibility to larkspur poisoning were used to assess selection of larkspur (<i>Delphinium occidentale</i>) while grazing. During July 2015, 2016, and 2017, diet selection of 12 cattle (6 susceptible, 6 resistant) was determined for 2 to 3 wk. During 2015 resistant steers ate 6% of their diets as total larkspur compared with 7% (<i>P</i> > 0.34) for susceptible steers. During 2016 there was a treatment × date interaction (<i>P</i> = 0.02) for total larkspur consumption; resistant steers consumed more larkspur on 5 trial days than did susceptible steers. Overall, resistant steers ate 6% of their diets as larkspur compared with 3% for susceptible steers. During 2017 there was a treatment × date interaction (<i>P</i> = 0.03) for total larkspur consumption; resistant heifers consumed more larkspur on 2 trial days than did susceptible heifers. Overall, during 2017 resistant heifers ate 7% of their diets as larkspur compared with 3% for susceptible heifers. The average serum concentration of methyllycaconitine in severely intoxicated, susceptible animals was approximately 700 ng/mL compared with approximately 1,000 ng/mL for severely intoxicated, resistant animals. The only fatalities (2) were in susceptible animals. The diet selection and comparative responses of resistant and susceptible animals on rangeland appear to validate the phenotyping done in the laboratory but must be verified in a controlled setting. Selecting resistant cattle to graze larkspur-infested rangelands may reduce losses; however, further research is required to develop genetic biomarkers to identify such animals.

Plains Larkspur (Delphinium geyeri) Grazing by Cattle in Wyoming

Plains larkspur (Delphinium geyeri Greene) is a major cause of cattle deaths in the northern Great Plains of Wyoming and Colorado. We examined the amount and timing of larkspur ingestion by grazing cattle in relation to larkspur phenology, nutrient concentrations, and weather conditions. Four summer grazing trials were conducted near Cheyenne (1996 and 1997) and Laramie, Wyo. (1998 and 1999). All trials began when plains larkspur was vegetative or in the early bud stage. In the first 2 studies, 6 yearling heifers grazed from 3 May to 4 August 1996; the same animals plus 5 cow-calf pairs grazed from 13 May to 10 August 1997. During both 1996 and 1997, cattle ate 0.5 to 1% of bites as larkspur during May, then consumption decreased to nearly 0 during the remainder of both summers. When eaten, larkspur was typically consumed during cool, foggy weather conditions. In the last 2 studies, 6 cow-calf pairs grazed near Laramie, Wyo., from 13 May to 30 June 1998, and 6 different cow-calf pairs grazed from 2 June to 20 July 1999. Cattle ate substantial amounts of plains larkspur (herd average approximately 3%) during the vegetative and bud stages from mid-May into early June, 1998. Cattle may have eaten more larkspur during 1998 because drought reduced spring availability of green grass. Consumption of larkspur was negatively related (r2 = 0.43) to daily temperature in 1998, but not during 1999. During 1999 cattle ate essentially no plains larkspur during the vegetative and bud stages, but ate larkspur (herd average approximately 5%) during the flower and pod stages when larkspur plants were beginning to desiccate and ambient temperatures were above average. This series of trials indicates that it will be difficult to predict plains larkspur consumption based on larkspur growth patterns or weather. Although cattle sometimes increase plains larkspur consumption when temperatures are cooler than normal, this pattern is not consistent enough to serve as a basis for management recommendations. DOI:10.2458/azu_jrm_v55i4_pfister

Plains larkspur (Delphinium geyeri) grazing by cattle in Wyoming

Plains larkspur (Delphinium geyeri Greene) is a major cause of cattle deaths in the northern Great Plains of Wyoming and Colorado. We examined the amount and timing of larkspur ingestion by grazing cattle in relation to larkspur phenology, nutrient concentrations, and weather conditions. Four summer grazing trials were conducted near Cheyenne (1996 and 1997) and Laramie, Wyo. (1998 and 1999). All trials began when plains larkspur was vegetative or in the early bud stage. In the first 2 studies, 6 yearling heifers grazed from 3 May to 4 August 1996; the same animals plus 5 cow-calf pairs grazed from 13 May to 10 August 1997. During both 1996 and 1997, cattle ate 0.5 to 1% of bites as larkspur during May, then consumption decreased to nearly 0 during the remainder of both summers. When eaten, larkspur was typically consumed during cool, foggy weather conditions. In the last 2 studies, 6 cow-calf pairs grazed near Laramie, Wyo., from 13 May to 30 June 1998, and 6 different cow-calf pairs grazed from 2 June to 20 July 1999. Cattle ate substantial amounts of plains larkspur (herd average approximately 3%) during the vegetative and bud stages from mid-May into early June, 1998. Cattle may have eaten more larkspur during 1998 because drought reduced spring availability of green grass. Consumption of larkspur was negatively related (r2 = 0.43) to daily temperature in 1998, but not during 1999. During 1999 cattle ate essentially no plains larkspur during the vegetative and bud stages, but ate larkspur (herd average approximately 5%) during the flower and pod stages when larkspur plants were beginning to desiccate and ambient temperatures were above average. This series of trials indicates that it will be difficult to predict plains larkspur consumption based on larkspur growth patterns or weather. Although cattle sometimes increase plains larkspur consumption when temperatures are cooler than normal, this pattern is not consistent enough to serve as a basis for management recommendations.

Tall Larkspur Ingestion: Can Cattle Regulate Intake Below Toxic Levels?

Tall larkspur (Delphinium barbeyi) is a toxic forb often consumed by cattle on mountain rangelands, with annual fatalities averaging about 5%. This study examined the relationship between food ingestion and toxicity in cattle. Two grazing studies suggested that larkspur consumption above 25–30% of cattle diets for one or two days led to reduced larkspur consumption on subsequent days. We subsequently hypothesized that cattle can generally limit intake of larkspur to sublethal levels. This hypothesis was tested by feeding a 27% larkspur pellet in experiment 1. Cattle given a 27% larkspur pellet ad libitum showed distinct cyclic patterns of intake, where increased larkspur consumption on one or two days was followed by reduced (P 0.05) between controls and treatment animals at the 20 or 40 mg LiCl/kg dose in the percentage of corn consumed, but the 80 mg LiCl/kg dose induced a cyclic response (mean 46%) compared to intake by controls (mean 96%) (P < 0.001). At the 80 mg/kg dose, LiCl induced an aversion to corn; when corn intake decreased on subsequent days and LiCl dose also decreased, cattle responded by increasing corn intake and apparently extinguishing the transient food aversion. Experiment 3 was similar to the LiCl trial, except that tall larkspur was the toxin. Cattle responded to oral gavage of ground larkspur with distinct cycles; days of higher corn consumption were followed by one to three days of reduced consumption. Corn intake for controls was higher (P < 0.01) than for larkspur-treated animals (means 84 and 52%, respectively; day × treatment interaction P < 0.01). The threshold for toxic effects on corn intake was 14 mg toxic alkaloid/kg body weight. In conclusion, cattle apparently limit ingestion of some toxins so that periods of high consumption are followed by periods of reduced consumption to allow for detoxification. Cyclic consumption generally enables cattle to regulate tall larkspur consumption below a toxic threshold and allows cattle the opportunity to safely use an otherwise nutritious, but toxic, plant.

Influence of alkaloid concentration on acceptability of tall larkspur (Delphinium spp.) to cattle and sheep

Tall larkspur (Delphinium spp.) is a serious toxic plant problem on western U.S. ranges. The major toxins in tall larkspur are methyllycaconitine (MLA) and 14-deacetylnudicauline (14-DAN); the sum of both is termed the toxic alkaloid concentration. Toxic alkaloids comprise about 20-50% of the total alkaloid concentration in tall larkspur. Toxic and total alkaloid concentration generally declines with maturity, whereas cattle and sheep consumption of larkspur typically increases with plant maturity. We hypothesized that cattle and sheep consumption of tall larkspur was negatively related to higher concentrations of total or toxic alkaloid. We compared consumption of several collections of dried, ground larkspur and fresh larkspur in a series of trials. In another trial, a crude alkaloid fraction was extracted with ethanol, added to alfalfa hay, and consumption compared to untreated alfalfa hay, alcohol-treated hay, and the essentially alkaloid-free plant residue. In all cases we correlated amounts eaten with total and toxic alkaloid concentration. A grazing trial was also conducted to relate larkspur consumption over time to alkaloid concentrations. Total alkaloid concentrations in dried, whole-plant collections ranged from 9.3 to 38.8 mg/g of dry weight, whereas toxic alkaloid concentrations varied from 0.0 to 7.1 mg/g. In one pen trial, cattle preferred a larkspur collection (P<0.01) that contained no toxic alkaloids but had a high total alkaloid concentration (39 mg/g). There was no correlation (P>0.05), however, between concentrations of total or toxic alkaloids and amount of dry plant consumed in this or any other trial. Conversely, sheep consumption tended to be negatively influenced by total and toxic alkaloid concentration (P≤0.08). In the trials with extract, cattle preferred the alcohol-treated hay and rejected the alkaloid-free residue (P<0.01), whereas the alkaloid-treated hay was of intermediate acceptability. Cattle preferred the alkaloid-treated hay over the alkaloid-free residue, indicating that alkaloids did not deter consumption. Conversely, the alkaloid-treated hay was less preferred than either untreated or alcohol-treated hay, suggesting a negative effect on acceptability. There was no correlation between alkaloid concentration and amount of treated feed eaten. In field trials, the amount of composited, fresh leaves or flowers eaten by cattle was influenced by plant part (P=0.04), but was not related (P>0.05) to alkaloid concentration. Cattle preferred leaves over flowers when offered individual plants differing in phenological stage and/or amount of shade, but alkaloid concentration was not related to consumption. We conclude that knowledge of the concentration of total or toxic alkaloid in tall larkspur will give little or no indication of plant acceptability to cattle. Even though accurate predictions can be made about the potential toxicity of larkspur based on the concentration of toxic alkaloids, predictions about consumption must be based primarily on plant phenology.

Effects of Carbachol Administration in Cattle Grazing Tall Larkspur-Infested Range

Tall larkspur (Delphinium barbeyi L. Huth.) toxicosis of cattle is a serious problem on western USA mountain rangelands. Manipulating the ruminal environment may decrease the susceptibility of cattle to larkspur intoxication. The cholinergic drug carbachol can greatly increase salivary flow and fluid passage rate in ruminants. Our objectives were to: (1) determine if chronic administration of carbachol altered ruminal fluid passage rate, ruminal pH, or water intake in grazing cattle, and (2) evaluate mineral salt supplementation as a prophylactic procedure for cattle grazing larkspur-infested rangelands. The study was conducted during summer of 1990 and 1991 near Yampa, Colo. Twelve heifers were divided randomly into 3 treatment groups: (1) carbachol administered at 0.01 mg.kg-1.day-1 via subcutaneous osmotic minipumps; (2) mineral-salt supplement dosed intraruminally at 0.25 g.kg-1.day-1; and (3) controls. Administration of carbachol either had no effect or a negative effect on ruminal fluid passage rate, ruminal pH, saliva production, and water intake compared with the controls. Carbachol had few consistent effects on serum electrolyte concentrations compared to the controls. Treatments did not influence cattle diet selection; cattle ate no larkspur during 1990, but selected larkspur for 16% of their diets during August, 1991. There was no indication that supplementation with mineral salt would attenuate larkspur toxicosis through increased dilution rates, or decreased larkspur consumption. Our results indicate that neither carbachol nor mineral supplementation will reduce animal susceptibility to larkspur toxicosis.

Storms Influence Cattle to Graze Larkspur: An Observation

Livestock producers report cattle deaths from larkspur (Delphinium spp.) poisoning increase during stormy periods. In controlled grazing studies, we observed cattle increase larkspur consumption during stormy weather. Periods of gluttonous larkspur consumption generally coincided with storms during a 1990 grazing study. Cattle consumed larkspur almost exclusively for 20-30 min periods during storms, as opposed to intermittent grazing of larkspur flowers, pods, and leaves. In 1991 weather parameters were measured and correlated with larkspur consumption. Larkspur consumption was negatively correlated with decreasing temperature and barometric pressure (r = -0.45 and -0.60 respectively); and positively correlated with increasing relative humidity, leaf wetness, and precipitation (r = 0.45, 0.74, and 0.27, respectively). Understanding consumption patterns of cattle grazing larkspur will aid in developing management strategies to reduce cattle deaths.

Prior Grazing by Sheep Reduces Waxy Larkspur Consumption by Cattle: An Observation

Sheep are more resistent to larkspur poisoning than cattle. Grazing larkspur with sheep before cattle turn-in may reduce the threat of cattle poisoning. Two 2.1-ha pastures were established in Upper Ruby Valley in southwest Montana in 1987 and 1989. A band of sheep grazed 1 pasture in mid-June in both years. Sheep grazed 70% of larkspur stalks in 1987 and 35% in 1988. Because sheep grazed little larkspur in 1988, larkspur was hand decapitated to simulate the use obtained in 1987 for the subsequent cattle grazing portion of the trial. Five cows were placed in each pasture immediately following sheep grazing in 1987 and after a 3-week delay in 1998. Cattle diets were quantified by bite counts. Waxy larkspur consumption by cattle in the sheep-grazed pasture was lower than in the cattle-only pasture especially during and after rainstorms in 1987 and throughout the study in 1988. One cow died from larkspur poisoning in the cattle-only pasture in 1988. If sheep will graze waxy larkspur, subsequent consumption by cattle can apparently be reduced on this site, thus reducing the risk of poisoning.

Toxicity of extracts of tall larkspur ( Delphinium barbeyi) in mice, hamsters, rats and sheep

Larkspur consumption is a major source of cattle losses on mountain and high plains rangelands of western North America. Our objective was to find a suitable laboratory animal model for measuring larkspur toxicity for subsequent use as an estimator of toxicity to cattle. The LD 50 for subcutaneous injection and for oral gavage of extract from Delphinium barbeyi, a highly toxic and troublesome rangeland tall larkspur, was compared for mice, hamsters, rats and sheep. Similarity of primary clinical signs of poisoning and lack of significant difference in slope of the dose-response curves implied that the overall effect of the larkspur alkaloids was the same for all rodent species tested. Sheep were the most susceptible to poisoning by subcutaneous injection of larkspur extract with decreasing susceptibility in hamsters, mice and rats, but sheep had least susceptibility when comparing response to oral (by gavage) doses. Also, death occurred rapidly after gavage as compared with subcutaneous doses in mice, hamsters and rats, but was nearly the same for sheep. We conclude that, of the animals tested, mice would be the best choice for a bioassay of the toxicity of larkspur because of their high susceptibility, rapid response time, and small dose requirement.

Mineral Salt Supplementation of Cattle Grazing Tall Larkspurinfested Rangeland during Drought

Mineral salt supplements are used in attempts to reduce cattle losses to tall larkspur (Delphinium spp.). We determined the effects of a mineral salt mix on larkspur consumption, ruminal fluid kinetics, and water intake during 4 periods in June, July, and August, 1988 (Trial 1), and during an 18-day grazing period in August, 1989 (Trial 2). In 1988, 12 ruminally cannulated heifers were divided into 3 treatment groups: control with no access to mineral (CONT), 0.5 g mineral (LOW), and 1.0 g mineral.kg body weight-1.day-1 (HIGH) dosed intraruminally. In 1989, 10 cows were allocated to either a control group or 0.75 g mineral.kg body weight-1.day-1. During Trials 1 and 2, consumption of larkspur peaked at 5 and 7% of cattle diets, respectively; these low levels were attributed to drought. There were no differences (P>0.1) in consumption of total larkspur or larkspur plant parts. Mineral supplement increased water consumption (P 0.05) among treatments during Trial 1, but FOR was increased by mineral treatment in Trial 2. Alkaloid concentration in larkspur declined with maturity, and was apparently elevated by drought in Trial 2. This study found little indication that mineral salt supplement altered the amount of larkspur consumed by grazing cattle. Increased water intake one summer did not alter ruminal fluid kinetics. If dietary minerals alter toxicity of larkspur to cattle, other mechanisms than those tested are responsible.

Effects of Phenology, Site, and Rumen Fill on Tall Larkspur Consumption by Cattle

Effects of Phenology, Site, and Rumen Fill on Tall Larkspur Consumption by Cattle